Traffic Flow Calculator (Greenshields)
Compute current speed, flow, maximum throughput and HCM Level of Service of a road from free-flow speed, jam density and current density using the Greenshields linear model.
How to Use the Traffic Flow Calculator (Greenshields)
- Enter free-flow speed.
- Enter jam density.
- Enter current density.
- Click Calculate.
使用例
- •Transport-engineering homework.
- •Preliminary road sizing.
- •Explaining level-of-service to stakeholders.
計算式
Greenshields: v = v_free × (1 − k/k_jam), q = v × k. Maximum: k_crit = k_jam/2, q_max = v_free × k_jam / 4.
よくある質問
What are typical values?
Urban arterial: v_free 50–60 km/h, k_jam 120–180 veh/km, q_max 1500–2500 veh/h/lane. Motorway: 110–130, 150–200, 2000–2400.
Is Greenshields accurate?
It is the simplest fundamental diagram and misses capacity drop and hysteresis. Use it for teaching and first-pass sizing; for design use HCM or a calibrated model.